The Static Persist load balancing method uses the persist mask, with the source IP address of the LDNS, in a deterministic algorithm to send requests to a specific pool member (virtual server). Using this method, BIG-IP® DNS sends DNS name resolution requests to the first available pool member based on a hash algorithm that determines the order of the pool members. This algorithm orders the pool members differently for each LDNS that is sending requests to BIG-IP DNS, taking into account the Classless Inter-Domain Routing (CIDR) of the LDNS. As BIG-IP DNS distributes requests across all pool members, requests from each LDNS (and thus, each client) are generally sent to the same pool member. When the selected pool member becomes unavailable, BIG-IP DNS sends requests to another pool member. When the original pool member becomes available again, BIG-IP DNS sends requests to that pool member.
You can configure BIG-IP® DNS to provide Static Persist load balancing of LDNS to virtual servers. With this configuration, BIG-IP DNS guarantees that certain transactions are routed through a single transaction manager, such as Local Traffic Manager™, or another server array manager. This is beneficial for transaction-oriented traffic, such as e-commerce shopping carts, online trading, and online banking.